DESCRIPTION (Provided by Applicant): Feline infectious peritonitis (FIP) is a deadly disease of domestic cats. FIP is thought to be caused by a virus that commonly infects cats without causing disease, but can occasionally mutate to become a deadly virus called feline infectious peritonitis virus (FIPV). The ability of the two virus types to infect different cells in the body is believed to be the difference in their ability to cause disease. Viruses must first bind to the surface of a cell before the virus can enter and replicate within the cell. Cell surface binding takes place through specific interactions between viral and cellular molecules. The binding interactions that allow FIPV to enter into cells is not well understood. The goal of this application is to characterize these interactions and determine some of the molecules involved. Upon completion of this work we will better understand how FIPV gains access to cells which is the first step in the virus infection cycle. Many anti-viral therapies target virus entry as a means to prevent virus infection and we expect the new knowledge generated here could contribute to the development of such therapies for FIP.